1. Field of the Invention
The present invention relates to an ink jet head of an ink jet printer, and more particularly, it relates to an ink jet head in which a plurality of ink nozzles are disposed along a sub scan direction in each of plural nozzle arrays disposed along a main scan direction.
2. Related Background Art
In recent years, ink jet printers have been generally popularized as printer apparatuses, and high speed printing and high quality printing of the printer have been requested. In a general ink jet printer, by shifting a print medium in a sub scan direction while shifting an ink jet head in a main scan direction, a dot matrix image is formed on the print medium by ink droplets discharged from the ink jet head.
In the general ink jet head, plural ink nozzles are disposed along the sub scan direction in a nozzle array, and, in a full-color ink jet head, first to third primary color nozzle arrays for individually discharging three primary color ink droplets are disposed side by side in the main scan direction. With this arrangement, although the ink jet head can form a color image having good color and a high resolving power at a high speed, nowadays, further high image quality has been requested. To this end, as means for printing the high quality image, there has been a technique in which dense ink and sparse ink are used as the same color ink. Further, although the high image quality can be achieved by decreasing a diameter of each ink nozzle, it is not desirable, because a print speed is reduced in comparison with the conventional technique if the nozzles are not disposed with high density and many nozzles are not prepared. Further, in many cases, although gradation expression achieved by changing an amount of the ink droplet is performed by using the same nozzle in the prior art, in order to permit the gradation using the same nozzle, it is difficult that the image quality is elevated to the lever achieved by using the dense and sparse inks due to limitation of arranging density and limitation of the small liquid droplet miniaturization caused by limitation of layouts of heat generating elements and wirings.